Four super water-stable lanthanide–organic frameworks with active uncoordinated carboxylic and pyridyl groups for selective luminescence sensing of Fe3+

Abstract

Four super water-stable isostructural lanthanide–organic frameworks, [Ln(HL)(H₂O)₂]_n·2H₂O (1-Ln) (Ln = Eu, Tb, Nd and Sm), have been successfully synthesized under hydrothermal conditions with 3,5-di(2,4-dicarboxylphenyl)pyridine (H₄L) and Ln(NO₃)₃·6H₂O. 1-Ln shows a novel 2D layered structure with uncoordinated carboxylic and pyridyl groups pointing to the interior of interlayer channels. The luminescent properties of 1-Eu in the solid state and one steeped in aqueous solution have been measured, which show excellent luminescence and good luminescent stability in water. Next 1-Eu was chosen as a probe for sensing different metal ions. Consequently, 1-Eu exhibits a highly selective response to Fe³⁺ through the luminescence quenching effect in aqueous solutions. The probable mechanisms of the quenching effects have been investigated in detail.